1. Sodium currents were studied using whole-cell voltage-clamp techniques in neurons acutely isol... more 1. Sodium currents were studied using whole-cell voltage-clamp techniques in neurons acutely isolated from superficial (II/III) and deep (V/VI) layers of guinea pig entorhinal cortex. 2. Sodium currents were larger (peak amplitude) in superficial than in deep layer cells under the same conditions: -1939 +/- 780 (SD) pA (N = 6) versus -307 +/- 257 pA (N = 6). Specific membrane conductance was calculated to be 12.3 +/- 9.6 mS/cm2 for superficial layer cells and 1.4 +/- 0.9 mS/cm2 for deep layer cells. 3. Sodium currents could be activated in superficial layer cells from potentials as depolarized as -20 mV, whereas no significant currents could be activated in deep neurons from potentials more depolarized than about -50 mV. Using a protocol consisting of a 25-ms prepulse and a 20 ms test pulse, the inactivation curves for superficial layer cells were found to be shifted toward more depolarized potentials by an average of 15 mV (V50 = -59.8 +/- 3.8 mV compared with -75.7 +/- 12.0 mV for deep cells). This produced a region of overlap with the activation curves for superficial cells. 4. Over a range of about -50 to -20 mV in superficial layer cells, the region of overlap of the activation and inactivation curves, a sodium current could be activated, which did not fully inactivate during the test pulse (average peak amplitude: -89.5 +/- 48.7 pA; crossover voltage: -39.2 +/- 2.0 mV). Voltage steps to more depolarized potentials, outside the voltage "window", permitted complete inactivation of the sodium current.(ABSTRACT TRUNCATED AT 250 WORDS)
1. Previous findings, such as the sensitivity of the hippocampal theta rhythm to cholinergic mani... more 1. Previous findings, such as the sensitivity of the hippocampal theta rhythm to cholinergic manipulation, support a "pacemaker" role for the cholinergic cells of the medial septal nucleus and the vertical limb of the nucleus of the diagonal band (MSN-NDB). To explore the mechanism(s) of action of systemic antimuscarinic drugs in eliminating the theta rhythm, recordings of hippocampal EEG and rhythmic MSN-NDB neurons that fired in phase with the hippocampal theta rhythm were taken during the administration of atropine in urethane-anesthetized rats. 2. Twenty-two of 33 rhythmic MSN-NDB cells continued to burst at the theta rhythm frequency after administration of a dose of atropine (25 mg/kg iv) that was sufficient to eliminate the theta rhythm (atropine-resistant cells). The remaining 11 cells lost their rhythmic firing pattern over the same time course as the loss of the theta rhythm (atropine-sensitive cells). 3. Both types of rhythmic MSN-NDB cells could be antidromically driven from the fimbria/fornix with similar latencies (range, 0.5-4.0 ms). The extracellularly recorded spike waveforms were not useful in predicting the atropine sensitivity of a given cell. Atropine-resistant cells frequently had higher firing rates than atropine-sensitive cells, but there was sufficient overlap of the two groups to make this a poor predictor of sensitivity. 4. Cooling the fimbria/fornix reversibly eliminated the hippocampal theta rhythm, but had no effect on 21/25 rhythmic MSN-NDB cells tested. This indicates that the atropine-sensitive MSN-NDB cells do not depend on the periodic output from the hippocampus for their rhythmic firing. Recordings from pairs of rhythmic MSN-NDB cells during cooling and/or atropine administration showed unchanged phase relations at the theta rhythm frequency. In rats in which the septohippocampal system was exposed by aspirating the overlying brain tissue, direct application of atropine (10 mg/ml) to the septal nuclei reversibly eliminated the hippocampal theta rhythm. 5. The rhythmic cells of the MSN-NDB are apparently composed of at least two distinct types, both of which potentially contribute to the production of the theta rhythm in the hippocampus. Elimination of hippocampal theta rhythm after local septal atropine application suggests that the loss of rhythmic activity in the group of atropine-sensitive septal cells is sufficient for the elimination of the theta rhythm. A model of the septohippocampal connections necessary for the theta rhythm is presented.
The mining and minerals processing industry requires assistance in decision making to support its... more The mining and minerals processing industry requires assistance in decision making to support its drive to sustainable development. To this end, a decision support framework (DSF) has been developed, guided by the tenets of Sustainability. This paper describes this DSF and its various components, which include tools for the formulation of techno-economic, environmental and socio-political objectives, and other tools of
Electroencephalography and Clinical Neurophysiology/Evoked Potentials Section, 1990
The effects of different orientations of a Cadwell round magnetic coil (MC) were compared with ea... more The effects of different orientations of a Cadwell round magnetic coil (MC) were compared with each other and with surface electrical stimulation of motor cortex in monkeys anesthetized with pentobarbital or urethane. Recordings were made from within the lateral corticospinal tract, either from axonal populations or with a microelectrode from individual axons. A lateral-sagittally orientated MC directly excited corticospinal neurons at lower stimulus intensity than was required for indirect, i.e., transsynaptic excitation via inputs to corticospinal neurons. By contrast, in 2 out of 3 macaques tested, a vertex-tangential orientation could excite corticospinal neurons indirectly at lower intensities than were required for direct excitation; at higher intensities, direct excitation also occurred. The site of direct corticospinal excitation by a lateral-sagittally orientated MC was inferred by comparing the response variability and latency to MC and surface electrical stimuli. Cathodal stimuli elicited more variable corticospinal population responses and later individual axonal responses than were obtained with anodal stimuli. The variability in response is attributed to interaction between nearby, on-going synaptic bombardment and the stimulus, implying that surface cathodal stimuli directly activate corticospinal neurons at the spike trigger zone (presumably the initial segment). By contrast, the consistency and reduced latency of the corticospinal responses to surface anodal stimuli are attributed to the direct excitation of corticospinal fibers within the white matter. When the stimulus intensity is clearly above threshold, surface anodal and cathodal stimuli can activate corticospinal neurons both directly and indirectly. Direct corticospinal excitation by the MC can resemble the effects of either surface anodal or surface cathodal stimuli. We conclude that the MC can activate corticospinal neurons at the spike trigger zone or their fibers deeper in white matter. The findings in the monkey are used to interpret the effects of different MC orientations in the human.
1. Intracellular recordings, taken from CAI pyramidal cells in guinea-pig hippocampal slices, wer... more 1. Intracellular recordings, taken from CAI pyramidal cells in guinea-pig hippocampal slices, were used to examine the origins of repetitive and burst firing in these cells. Single action potentials were elicited by depolarizing current injection at somatic recording sites. In contrast, current injection during intradendritic recordings initiated burst firing in the dendrites. Burst firing could be elicited in the soma by direct depolarization of distal apical dendrites (> 150 gm from the cell body layer) with large extracellular polarizing electrodes.
A cross-sectional analytic study was conducted. To collect normative data on back extensor endura... more A cross-sectional analytic study was conducted. To collect normative data on back extensor endurance holding times and evaluate the discriminative validity of the Biering-Sorensen test in a group of coal miners in Australia. Low back pain is a common complaint among those working in the Australian coal mining industry. One test that may be predictive of first-time episodes of low back pain is the Biering-Sorensen test of back extensor endurance strength. While this test has been evaluated in overseas sedentary populations, normative data and the discriminative ability of the test have not been evaluated with coal miners. Eighty-eight coal miners completed a questionnaire for known risk factors for low back pain, performed the Biering-Sorensen test, and undertook a test of aerobic fitness. Data analysis was performed to describe the groups and to determine whether any significant difference existed between those with a past history of low back pain and those without. Significantly lo...
ABSTRACT We present an instrument for simultaneous imaging of the rodent brain with frequency-dom... more ABSTRACT We present an instrument for simultaneous imaging of the rodent brain with frequency-domain optical tomography and magnetic resonance imaging. The instrument uses a custom-built fiber optic probe that allows for measurements in backreflectance geometry. The probe consists of 13 source and 26 detector fibers and is small enough to fit inside of a microMRI RF coil with an inner diameter of 38mm. Illumination by the source fibers is time demultiplexed by an optical fiber switch. A gain-modulated image intensifier CCD camera focuses onto the endpoints of large-core gradedindex detector fibers and collects the frequency-domain data. Imaging can be performed with source-modulation frequencies up to 1 GHz. The instrument is capable of acquiring multi-frequency optical tomography data at 2 wavelengths, and the data can be used to generate 3D maps of hemoglobin concentrations. At the same time magnetic resonance images can be acquired with in-plane resolution smaller than 100 micron. To illustrate the performance of the instrument we show results of small animal studies that involve inhalation of 100% carbogen and chemically induced seizures.
Whiplash-associated disorders are common and incur considerable expense in social and economic te... more Whiplash-associated disorders are common and incur considerable expense in social and economic terms. There are no known effective treatments for those people whose pain and disability persist beyond 3 months. We conducted a randomized, assessorblinded, controlled trial at two centres in Australia. All participants received 3 advice sessions. In addition the experimental group participated in 12 exercise sessions over 6 weeks. Primary outcomes were pain intensity, pain bothersomeness and function measured at 6 weeks and 12 months. Exercise and advice was more effective than advice alone at 6 weeks for all primary outcomes but not at 12 months. The effect of exercise on the 0-10 pain intensity scale was À1.1 (95%CI À1.8 to À0.3, p = 0.005) at 6 weeks and À0.2 (0.6 to À1.0, p = 0.59) at 12 months; on the bothersomeness scale the effect was À1.0 (À1.9 to À0.2, p = 0.003) at 6 weeks and 0.3 (À0.6 to 1.3, p = 0.48) at 12 months. The effect on function was 0.9 (0.3 to 1.6, p = 0.006) at 6 weeks and 0.6 (À0.1 to 1.4, p = 0.10) at 12 months. High levels of baseline pain intensity were associated with greater treatment effects at 6 weeks and high levels of baseline disability were associated with greater treatment effects at 12 months. In the short-term exercise and advice is slightly more effective than advice alone for people with persisting pain and disability following whiplash. Exercise is more effective for subjects with higher baseline pain and disability. Ó
Rocky Mountain Oil & Gas Technology Symposium, 2007
Copyright 2007, Society of Petroleum Engineers This paper was prepared for presentation at the 20... more Copyright 2007, Society of Petroleum Engineers This paper was prepared for presentation at the 2007 SPE Rocky Mountain Oil & Gas Technology Symposium held in Denver, Colorado, USA, 1618 April 2007. This paper was selected for presentation by an SPE Program ...
This paper describes implementation of a technique used to obtain a high fidelity fluid-thermal-s... more This paper describes implementation of a technique used to obtain a high fidelity fluid-thermal-structural solution of a combined cycle engine at its scram design point. Single-discipline simulations are insufficient here since interactions from other disciplines are significant. Using off-the-shelf, validated solvers for the fluid, chemistry, thermal, and structural solutions, this approach couples together their results to obtain consistent solutions.
The hippocampal theta rhythm (rhythmical slow activity, RSA) is one of the most thoroughly studie... more The hippocampal theta rhythm (rhythmical slow activity, RSA) is one of the most thoroughly studied EEG phenomena. Much of this experimental interest has been stimulated by suggestions that the mnemonic functions of the hippocampus may depend upon theta-related neuronal activity. Inputs from the medial septal nuclei to the hippocampus were shown to be essential for the theta rhythm in the 1950s, but the role of these basal forebrain projections has not been clearly defined. Four models of the septo-hippocampal connections involved in theta rhythm production are reviewed as the precise roles of these projections are discussed. In our final, consolidated model both cholinergic and GABAergic septal projection cells fire in rhythmic bursts that entrain hippocampal interneurons. The resulting rhythmic inhibition of hippocampal projection cells, together with their excitatory interconnections, generates at least one component of the theta rhythm.
1. In the hippocampal formation in vivo, brief periods of ã-frequency activity follow population ... more 1. In the hippocampal formation in vivo, brief periods of ã-frequency activity follow population bursts called sharp waves. The •200 Hz activity of the sharp wave itself may serve to enhance synaptic connections and the •40 Hz ã activity has been offered as a mechanism for solving the 'binding' problem. We describe epochs of ã-frequency activity which follow population spikes evoked by low frequency repetitive extracellular stimuli in retrohippocampal neurons of horizontal rat brain slices. 2. ã-Frequency activity recorded intracellularly from deep layer neurons of entorhinal cortex, presubiculum and parasubiculum consisted of one action potential correlated with each of the three to five ã cycles recorded with a proximate field potential electrode. A minority of cells exhibited only sub-threshold ã-frequency membrane potential oscillations (ranging from 5 to 10 mV). No cells fired more than one spike per ã cycle under any conditions. 3. The range of synchrony varied from individual cells which showed ã-frequency firing without corresponding oscillations in close field recordings to field potential recordings of oscillations which were well correlated across regions. The lead or lag between any two retrohippocampal regions was in the direction of the conduction delay for the primary population spike, but typically was less, and approached zero milliseconds for some cycles in most cells. The level of synchrony was stable for particular stimulating conditions (intensity, stimulation rate, stimulus location). 4. The duration of the period of ã activity had the duration of a slow depolarizing potential which was mediated by NMDA receptor activation. NMDA receptor antagonists or low concentrations of AMPA receptor antagonists reduced the duration of, or completely abolished the slow potential, thereby eliminating the ã portion of the evoked response. 5. ã-Frequency firing was eliminated by the GABAA receptor antagonist picrotoxin but small (< 5 mV) membrane potential oscillations remained after focal picrotoxin applications, and these exhibited the voltage dependence of EPSPs. Bath application of thiopental lowered the frequency of ã oscillations, confirming the involvement of GABAA receptors. 6. The GABAB receptor antagonist 2-hydroxy-saclofen appeared to enhance the ã activity by increasing the duration of the ã epoch and increasing the amplitude of individual ã cycles in field potential recordings. These saclofen-induced cycles were, however, less well synchronized across regions. 7. We show that synchronous ã (40-100 Hz) activity follows population bursts by deep layer retrohippocampal neurons in undrugged slices from rat brain. Responses from medial entorhinal, parasubicular or presubicular cells were not distinguishable. These events can be initiated by a propagating population spike. We suggest that an NMDA receptor mediated depolarization enables the network of deep layer retrohippocampal neurons to oscillate by providing a sustained excitation, the duration of which determines the duration of the ã episode. ã-Frequency firing is primarily the result of GABAA receptor dependent inhibition during this period of sustained depolarization. Recurrent excitation appears to be inconsequential for principal cell firing, but may contribute to interneuron firing. 7577
CA3 and subiculum are hippocampal formation regions that can initiate seizure activity because ea... more CA3 and subiculum are hippocampal formation regions that can initiate seizure activity because each has a substantial intrinsic excitatory connectivity. We studied the intrinsic connectivity of area CA1 by exploring the spread of synchronous population discharges in ventral hippocampal slices from rats using a recording chamber that permitted multiple simultaneous extracellular recordings along all laminae of CA1. Brief single stimulus pulses were applied to stratum oriens (SO) or stratum radiatum (SR) on the CA3 side or the subicular side of CA1. In disinhibited slices, events triggered with SO or SR stimulation on the CA3-side propagated over the proximo-distal extent of CA1 with a maximal conduction velocity of 0.4 m/s, comparable with antidromic conduction velocities within CA1. By contrast, SO or SR stimuli applied on the subicular side of CA1 triggered events that did not spread ''backward'' toward CA3. These events are rapidly decremented in amplitude and duration. Whereas antidromic responses were largest when stimuli were applied on the subicular side of CA1, such responses were not sufficient to trigger epileptiform discharges when excitatory transmission was intact. We conclude that the unidirectional spread of epileptiform activity in area CA1 is the result of an intrinsic axon collateral system where each pyramidal cell has a proportionally larger projection toward subiculum. Although this collateral system is sparse compared with other hippocampal formation regions, its unidirectionality protects against re-entrant activation of CA3 and may be physiologically significant as a relay from proximal CA1 to distal CA1. V
1. Sodium currents were studied using whole-cell voltage-clamp techniques in neurons acutely isol... more 1. Sodium currents were studied using whole-cell voltage-clamp techniques in neurons acutely isolated from superficial (II/III) and deep (V/VI) layers of guinea pig entorhinal cortex. 2. Sodium currents were larger (peak amplitude) in superficial than in deep layer cells under the same conditions: -1939 +/- 780 (SD) pA (N = 6) versus -307 +/- 257 pA (N = 6). Specific membrane conductance was calculated to be 12.3 +/- 9.6 mS/cm2 for superficial layer cells and 1.4 +/- 0.9 mS/cm2 for deep layer cells. 3. Sodium currents could be activated in superficial layer cells from potentials as depolarized as -20 mV, whereas no significant currents could be activated in deep neurons from potentials more depolarized than about -50 mV. Using a protocol consisting of a 25-ms prepulse and a 20 ms test pulse, the inactivation curves for superficial layer cells were found to be shifted toward more depolarized potentials by an average of 15 mV (V50 = -59.8 +/- 3.8 mV compared with -75.7 +/- 12.0 mV for deep cells). This produced a region of overlap with the activation curves for superficial cells. 4. Over a range of about -50 to -20 mV in superficial layer cells, the region of overlap of the activation and inactivation curves, a sodium current could be activated, which did not fully inactivate during the test pulse (average peak amplitude: -89.5 +/- 48.7 pA; crossover voltage: -39.2 +/- 2.0 mV). Voltage steps to more depolarized potentials, outside the voltage &quot;window&quot;, permitted complete inactivation of the sodium current.(ABSTRACT TRUNCATED AT 250 WORDS)
1. Previous findings, such as the sensitivity of the hippocampal theta rhythm to cholinergic mani... more 1. Previous findings, such as the sensitivity of the hippocampal theta rhythm to cholinergic manipulation, support a &quot;pacemaker&quot; role for the cholinergic cells of the medial septal nucleus and the vertical limb of the nucleus of the diagonal band (MSN-NDB). To explore the mechanism(s) of action of systemic antimuscarinic drugs in eliminating the theta rhythm, recordings of hippocampal EEG and rhythmic MSN-NDB neurons that fired in phase with the hippocampal theta rhythm were taken during the administration of atropine in urethane-anesthetized rats. 2. Twenty-two of 33 rhythmic MSN-NDB cells continued to burst at the theta rhythm frequency after administration of a dose of atropine (25 mg/kg iv) that was sufficient to eliminate the theta rhythm (atropine-resistant cells). The remaining 11 cells lost their rhythmic firing pattern over the same time course as the loss of the theta rhythm (atropine-sensitive cells). 3. Both types of rhythmic MSN-NDB cells could be antidromically driven from the fimbria/fornix with similar latencies (range, 0.5-4.0 ms). The extracellularly recorded spike waveforms were not useful in predicting the atropine sensitivity of a given cell. Atropine-resistant cells frequently had higher firing rates than atropine-sensitive cells, but there was sufficient overlap of the two groups to make this a poor predictor of sensitivity. 4. Cooling the fimbria/fornix reversibly eliminated the hippocampal theta rhythm, but had no effect on 21/25 rhythmic MSN-NDB cells tested. This indicates that the atropine-sensitive MSN-NDB cells do not depend on the periodic output from the hippocampus for their rhythmic firing. Recordings from pairs of rhythmic MSN-NDB cells during cooling and/or atropine administration showed unchanged phase relations at the theta rhythm frequency. In rats in which the septohippocampal system was exposed by aspirating the overlying brain tissue, direct application of atropine (10 mg/ml) to the septal nuclei reversibly eliminated the hippocampal theta rhythm. 5. The rhythmic cells of the MSN-NDB are apparently composed of at least two distinct types, both of which potentially contribute to the production of the theta rhythm in the hippocampus. Elimination of hippocampal theta rhythm after local septal atropine application suggests that the loss of rhythmic activity in the group of atropine-sensitive septal cells is sufficient for the elimination of the theta rhythm. A model of the septohippocampal connections necessary for the theta rhythm is presented.
The mining and minerals processing industry requires assistance in decision making to support its... more The mining and minerals processing industry requires assistance in decision making to support its drive to sustainable development. To this end, a decision support framework (DSF) has been developed, guided by the tenets of Sustainability. This paper describes this DSF and its various components, which include tools for the formulation of techno-economic, environmental and socio-political objectives, and other tools of
Electroencephalography and Clinical Neurophysiology/Evoked Potentials Section, 1990
The effects of different orientations of a Cadwell round magnetic coil (MC) were compared with ea... more The effects of different orientations of a Cadwell round magnetic coil (MC) were compared with each other and with surface electrical stimulation of motor cortex in monkeys anesthetized with pentobarbital or urethane. Recordings were made from within the lateral corticospinal tract, either from axonal populations or with a microelectrode from individual axons. A lateral-sagittally orientated MC directly excited corticospinal neurons at lower stimulus intensity than was required for indirect, i.e., transsynaptic excitation via inputs to corticospinal neurons. By contrast, in 2 out of 3 macaques tested, a vertex-tangential orientation could excite corticospinal neurons indirectly at lower intensities than were required for direct excitation; at higher intensities, direct excitation also occurred. The site of direct corticospinal excitation by a lateral-sagittally orientated MC was inferred by comparing the response variability and latency to MC and surface electrical stimuli. Cathodal stimuli elicited more variable corticospinal population responses and later individual axonal responses than were obtained with anodal stimuli. The variability in response is attributed to interaction between nearby, on-going synaptic bombardment and the stimulus, implying that surface cathodal stimuli directly activate corticospinal neurons at the spike trigger zone (presumably the initial segment). By contrast, the consistency and reduced latency of the corticospinal responses to surface anodal stimuli are attributed to the direct excitation of corticospinal fibers within the white matter. When the stimulus intensity is clearly above threshold, surface anodal and cathodal stimuli can activate corticospinal neurons both directly and indirectly. Direct corticospinal excitation by the MC can resemble the effects of either surface anodal or surface cathodal stimuli. We conclude that the MC can activate corticospinal neurons at the spike trigger zone or their fibers deeper in white matter. The findings in the monkey are used to interpret the effects of different MC orientations in the human.
1. Intracellular recordings, taken from CAI pyramidal cells in guinea-pig hippocampal slices, wer... more 1. Intracellular recordings, taken from CAI pyramidal cells in guinea-pig hippocampal slices, were used to examine the origins of repetitive and burst firing in these cells. Single action potentials were elicited by depolarizing current injection at somatic recording sites. In contrast, current injection during intradendritic recordings initiated burst firing in the dendrites. Burst firing could be elicited in the soma by direct depolarization of distal apical dendrites (> 150 gm from the cell body layer) with large extracellular polarizing electrodes.
A cross-sectional analytic study was conducted. To collect normative data on back extensor endura... more A cross-sectional analytic study was conducted. To collect normative data on back extensor endurance holding times and evaluate the discriminative validity of the Biering-Sorensen test in a group of coal miners in Australia. Low back pain is a common complaint among those working in the Australian coal mining industry. One test that may be predictive of first-time episodes of low back pain is the Biering-Sorensen test of back extensor endurance strength. While this test has been evaluated in overseas sedentary populations, normative data and the discriminative ability of the test have not been evaluated with coal miners. Eighty-eight coal miners completed a questionnaire for known risk factors for low back pain, performed the Biering-Sorensen test, and undertook a test of aerobic fitness. Data analysis was performed to describe the groups and to determine whether any significant difference existed between those with a past history of low back pain and those without. Significantly lo...
ABSTRACT We present an instrument for simultaneous imaging of the rodent brain with frequency-dom... more ABSTRACT We present an instrument for simultaneous imaging of the rodent brain with frequency-domain optical tomography and magnetic resonance imaging. The instrument uses a custom-built fiber optic probe that allows for measurements in backreflectance geometry. The probe consists of 13 source and 26 detector fibers and is small enough to fit inside of a microMRI RF coil with an inner diameter of 38mm. Illumination by the source fibers is time demultiplexed by an optical fiber switch. A gain-modulated image intensifier CCD camera focuses onto the endpoints of large-core gradedindex detector fibers and collects the frequency-domain data. Imaging can be performed with source-modulation frequencies up to 1 GHz. The instrument is capable of acquiring multi-frequency optical tomography data at 2 wavelengths, and the data can be used to generate 3D maps of hemoglobin concentrations. At the same time magnetic resonance images can be acquired with in-plane resolution smaller than 100 micron. To illustrate the performance of the instrument we show results of small animal studies that involve inhalation of 100% carbogen and chemically induced seizures.
Whiplash-associated disorders are common and incur considerable expense in social and economic te... more Whiplash-associated disorders are common and incur considerable expense in social and economic terms. There are no known effective treatments for those people whose pain and disability persist beyond 3 months. We conducted a randomized, assessorblinded, controlled trial at two centres in Australia. All participants received 3 advice sessions. In addition the experimental group participated in 12 exercise sessions over 6 weeks. Primary outcomes were pain intensity, pain bothersomeness and function measured at 6 weeks and 12 months. Exercise and advice was more effective than advice alone at 6 weeks for all primary outcomes but not at 12 months. The effect of exercise on the 0-10 pain intensity scale was À1.1 (95%CI À1.8 to À0.3, p = 0.005) at 6 weeks and À0.2 (0.6 to À1.0, p = 0.59) at 12 months; on the bothersomeness scale the effect was À1.0 (À1.9 to À0.2, p = 0.003) at 6 weeks and 0.3 (À0.6 to 1.3, p = 0.48) at 12 months. The effect on function was 0.9 (0.3 to 1.6, p = 0.006) at 6 weeks and 0.6 (À0.1 to 1.4, p = 0.10) at 12 months. High levels of baseline pain intensity were associated with greater treatment effects at 6 weeks and high levels of baseline disability were associated with greater treatment effects at 12 months. In the short-term exercise and advice is slightly more effective than advice alone for people with persisting pain and disability following whiplash. Exercise is more effective for subjects with higher baseline pain and disability. Ó
Rocky Mountain Oil & Gas Technology Symposium, 2007
Copyright 2007, Society of Petroleum Engineers This paper was prepared for presentation at the 20... more Copyright 2007, Society of Petroleum Engineers This paper was prepared for presentation at the 2007 SPE Rocky Mountain Oil & Gas Technology Symposium held in Denver, Colorado, USA, 1618 April 2007. This paper was selected for presentation by an SPE Program ...
This paper describes implementation of a technique used to obtain a high fidelity fluid-thermal-s... more This paper describes implementation of a technique used to obtain a high fidelity fluid-thermal-structural solution of a combined cycle engine at its scram design point. Single-discipline simulations are insufficient here since interactions from other disciplines are significant. Using off-the-shelf, validated solvers for the fluid, chemistry, thermal, and structural solutions, this approach couples together their results to obtain consistent solutions.
The hippocampal theta rhythm (rhythmical slow activity, RSA) is one of the most thoroughly studie... more The hippocampal theta rhythm (rhythmical slow activity, RSA) is one of the most thoroughly studied EEG phenomena. Much of this experimental interest has been stimulated by suggestions that the mnemonic functions of the hippocampus may depend upon theta-related neuronal activity. Inputs from the medial septal nuclei to the hippocampus were shown to be essential for the theta rhythm in the 1950s, but the role of these basal forebrain projections has not been clearly defined. Four models of the septo-hippocampal connections involved in theta rhythm production are reviewed as the precise roles of these projections are discussed. In our final, consolidated model both cholinergic and GABAergic septal projection cells fire in rhythmic bursts that entrain hippocampal interneurons. The resulting rhythmic inhibition of hippocampal projection cells, together with their excitatory interconnections, generates at least one component of the theta rhythm.
1. In the hippocampal formation in vivo, brief periods of ã-frequency activity follow population ... more 1. In the hippocampal formation in vivo, brief periods of ã-frequency activity follow population bursts called sharp waves. The •200 Hz activity of the sharp wave itself may serve to enhance synaptic connections and the •40 Hz ã activity has been offered as a mechanism for solving the 'binding' problem. We describe epochs of ã-frequency activity which follow population spikes evoked by low frequency repetitive extracellular stimuli in retrohippocampal neurons of horizontal rat brain slices. 2. ã-Frequency activity recorded intracellularly from deep layer neurons of entorhinal cortex, presubiculum and parasubiculum consisted of one action potential correlated with each of the three to five ã cycles recorded with a proximate field potential electrode. A minority of cells exhibited only sub-threshold ã-frequency membrane potential oscillations (ranging from 5 to 10 mV). No cells fired more than one spike per ã cycle under any conditions. 3. The range of synchrony varied from individual cells which showed ã-frequency firing without corresponding oscillations in close field recordings to field potential recordings of oscillations which were well correlated across regions. The lead or lag between any two retrohippocampal regions was in the direction of the conduction delay for the primary population spike, but typically was less, and approached zero milliseconds for some cycles in most cells. The level of synchrony was stable for particular stimulating conditions (intensity, stimulation rate, stimulus location). 4. The duration of the period of ã activity had the duration of a slow depolarizing potential which was mediated by NMDA receptor activation. NMDA receptor antagonists or low concentrations of AMPA receptor antagonists reduced the duration of, or completely abolished the slow potential, thereby eliminating the ã portion of the evoked response. 5. ã-Frequency firing was eliminated by the GABAA receptor antagonist picrotoxin but small (< 5 mV) membrane potential oscillations remained after focal picrotoxin applications, and these exhibited the voltage dependence of EPSPs. Bath application of thiopental lowered the frequency of ã oscillations, confirming the involvement of GABAA receptors. 6. The GABAB receptor antagonist 2-hydroxy-saclofen appeared to enhance the ã activity by increasing the duration of the ã epoch and increasing the amplitude of individual ã cycles in field potential recordings. These saclofen-induced cycles were, however, less well synchronized across regions. 7. We show that synchronous ã (40-100 Hz) activity follows population bursts by deep layer retrohippocampal neurons in undrugged slices from rat brain. Responses from medial entorhinal, parasubicular or presubicular cells were not distinguishable. These events can be initiated by a propagating population spike. We suggest that an NMDA receptor mediated depolarization enables the network of deep layer retrohippocampal neurons to oscillate by providing a sustained excitation, the duration of which determines the duration of the ã episode. ã-Frequency firing is primarily the result of GABAA receptor dependent inhibition during this period of sustained depolarization. Recurrent excitation appears to be inconsequential for principal cell firing, but may contribute to interneuron firing. 7577
CA3 and subiculum are hippocampal formation regions that can initiate seizure activity because ea... more CA3 and subiculum are hippocampal formation regions that can initiate seizure activity because each has a substantial intrinsic excitatory connectivity. We studied the intrinsic connectivity of area CA1 by exploring the spread of synchronous population discharges in ventral hippocampal slices from rats using a recording chamber that permitted multiple simultaneous extracellular recordings along all laminae of CA1. Brief single stimulus pulses were applied to stratum oriens (SO) or stratum radiatum (SR) on the CA3 side or the subicular side of CA1. In disinhibited slices, events triggered with SO or SR stimulation on the CA3-side propagated over the proximo-distal extent of CA1 with a maximal conduction velocity of 0.4 m/s, comparable with antidromic conduction velocities within CA1. By contrast, SO or SR stimuli applied on the subicular side of CA1 triggered events that did not spread ''backward'' toward CA3. These events are rapidly decremented in amplitude and duration. Whereas antidromic responses were largest when stimuli were applied on the subicular side of CA1, such responses were not sufficient to trigger epileptiform discharges when excitatory transmission was intact. We conclude that the unidirectional spread of epileptiform activity in area CA1 is the result of an intrinsic axon collateral system where each pyramidal cell has a proportionally larger projection toward subiculum. Although this collateral system is sparse compared with other hippocampal formation regions, its unidirectionality protects against re-entrant activation of CA3 and may be physiologically significant as a relay from proximal CA1 to distal CA1. V
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Papers by Mark Stewart